If you believe you have found a security vulnerability in Microflow, please report it privately — do not open a public issue.

Email mail@sanderboer.nl with:

• a description of the issue and its impact,
• steps to reproduce (a proof of concept if you have one),
• the affected component, version, or commit.

You can expect an acknowledgement within 5 business days and, where the report is valid, a remediation plan and a coordinated disclosure timeline. We will credit reporters who wish to be named once a fix is released.

Microflow runs partly on the user's own machine (desktop app, browser with Web Serial) and connects to hardware and to cloud endpoints the user configures (LLM providers, MQTT brokers, and the Figma and Penpot plugins). Of particular interest:

• handling of user-supplied credentials (broker passwords, API keys),
• the serial / Firmata transport and device interaction,
• cloud request handling (LLM/MQTT/Figma) and the browser's direct-to-endpoint calls,
• the design-tool bridge: the Figma and Penpot plugins and the MQTT protocol they share with Studio (packages/design-bridge),
• the collaboration sync layer.

Note: by design, the browser host talks directly to the cloud endpoints a user configures (no proxy — see ADR-0009); users are responsible for the endpoints they point Microflow at.

The Figma and Penpot plugins link a design file to Studio over an MQTT broker the user chooses (ADR-0028). By design:

• The Bridge ID is the only separation on a shared broker. Every bridge topic is microflow/{bridgeId}/…. On a public broker, such as the plugins' default test.mosquitto.org, anyone who knows or guesses a Bridge ID can read the variable list (retained on the broker) and the values, and can publish set messages that change the open design file. Studio's default Bridge ID is derived from the account display name, so it is guessable. Use a private broker with authentication for anything sensitive.
• Broker credentials are stored in plain text. The Figma plugin keeps its broker URL, username and password in Figma's clientStorage; the Penpot plugin keeps them in the localStorage of its UI page.
• The Figma plugin may reach any domain. Its manifest sets networkAccess.allowedDomains to ["*"], so it can connect to whichever broker the user enters.
• Certificate checks. @microflow/mqtt, the plugins' MQTT client, passes rejectUnauthorized: false for ws/wss connections. Both plugins run in a browser, where the browser's own WebSocket TLS check applies; outside a browser this option would turn certificate verification off.

Microflow is under active development. Security fixes target the latest release and main. Older versions are not maintained.

Vulnerabilities in third-party hardware, user-configured brokers/LLM endpoints, or the user's own network are outside this project's control, though we're happy to hear about issues that affect how Microflow interacts with them.